CT理论与应用研究

Research on Accelerating MLS-EM Reconstruction Algorithm for Cosmic Ray Muon Radiography

LIU Yuan-yuan, ZHAO Zi-ran, CHEN Zhi-qiang, ZHANG Li, TU Chao

2007, 16(3): 1-5.

Abstract(843) PDF(1)

Abstract:
Cosmic ray muon radiography which has a good penetrability and sensitivity to high-Z materials is an effective way for detecting shielded nuclear materials.Reconstruction algorithm is the key point of this technique.Now,MLS-EM reconstruction algorithm is a better one than other existing radiographic methods.However,its reconstruction time is too long to let it be used into a real detective system.Because of that,based on the characteristics of the muon radiography system,this paper proposed a good method to accelerate MLS-EM.It used the POCA algorithm as the initial value of the EM,and then accelerated the algorithm using the function of the OS.Finially,the simulation experiments demonstrated that this method could effectively accelerate MLS-EM.Therefore,it played a significant role to do a further step to let the technique of cosmic muon radiography into our real life.

Splatting Algorithm Apply to Algebraic Arithmetic of Three Dimensional Computer Tomography

MO Hui-yun, PAN Jin-xiao

2007, 16(3): 6-12.

Abstract(882) PDF(3)

Abstract:
This thesis uses ART(algebraic reconstruction technique) to reconstruct 3-D objects,Based on Splatting theory it presents a method of calculating ART weighting coefficients to enhance spatial resolution.This algorithm is based on the 3-D cone-beam scanning,using cubic B spline local basis function as interpolate kernel,and utilizing footprint function of filter kernel to interpolate the volume to calculate the weighting coefficients.Compared with the constant-size interpolation,the algebraic can gain more accurate object gray values.In the same experiment condition it can reconstruct high-resolution object.In the thesis,it gives the practical realization of splatting algebraic adapting to 3-D cone-beam reconstruction,and uses the experiment data to reconstruct the real object and analyze the error.

The Study of Cone-Beam ART Algorithm Using Parallel Computing

LIU Chun-hua, PAN Jin-xiao

2007, 16(3): 13-19.

Abstract(897) PDF(2)

Abstract:
In order to solve the problem that the computing time of ART is too long,we rewrite the algorithm into parallel format and run it on the PC cluster.By parallel computing,the speedup factor is roughly equal to the number of CPUs and the precision of reconstruction is the same.This technique is very suitable for real-time reconstruction with iterative methods.

Principles and Implementation of Visualization on 3D Seismic Data Volume

ZHANG Er-hua, GAO Lin, MA Ren-an, YANG Jing-yu

2007, 16(3): 20-28.

Abstract(682) PDF(0)

Abstract:
Visualization is effective for true 3-D interpretation of 3-D seismic data volume.This paper introduces the basic principles of visualization on 3-D seismic data volume,and the main steps using ray-casting algorithm,develops the computing formulas to compose visualization image,discusses the physical meaning of opacity curve and its adjusting function to visualization image.The results of real cases showed the geologic body can be directly imaged from original 3-D seismic data volume by this method.The scattered,isolated information can be related together to reveal the geologic phenomenon and regular hidden in data.

Obtainment of the Geometrical Parameters of Two Dimensional Contour in Reverse Engineering based on Industrial Computerized Tomography

WANG Yan-fang, LIU Li, QUE Jie-min, YAN Yong-lian

2007, 16(3): 29-35.

Abstract(886) PDF(1)

Abstract:
Recently,one of research emphases in Reverse Engineering field based on Industrial Computerized Tomography is to obtain the characteristic parameters of an object’s contours.In this article,we improve the track algorithm of ICT contours for extracting the object’s contours rapidly and precisely,and then use vectorization technology to accomplish the geometrical characteristic recognition of 2D contours at any position or any direction from the CT images,and obtain the geometrical parameters of the contours at the same time.These algorithms are integrated into a specialized and practical Reverse Engineering software system.

Thickness Evaluation of Pipes Using X-ray Real-time Radiographs

YUAN Pei-xin, NIU Yan-ping

2007, 16(3): 36-42.

Abstract(625) PDF(1)

Abstract:
Along with the fast development of NDT,X-ray Real-time radiographic method obtains great application.This paper discussed X-ray Real-time Radiographs detecting method research on insulated pipes,and this text emphasizes the experimental method of determining corrupt thickness of pipes and establishes the thickness mathematic model of the pipes.Consequently,we can make sure the corrupt thickness of pipes.The measurable research about pipe corrupt thickness helps to evaluate the safety of pipes and discover the hidden trouble in time.

The Primary Experimental Study of Thermal Neutron Tomography in SPRR-300

TANG Bin, ZHANG Song-bao, HUO He-yong, WU Yang, LIU Bin

2007, 16(3): 43-49.

Abstract(808) PDF(3)

Abstract:
Thermal neutron radiography is a useful complementary tool of the other non-destructive testing methods for the hydrogenous materials and heavy metal subassembly,and thermal neutron tomography has not been developed in China.By the use of the CCD-based thermal neutron digital radiography facility in SPRR-300 reactor and the Al column sample with holes,the projecting data of 36 multiplied 552 groups are collected.After and before the data are processed,the tomography image is gotten by the filter anti-projection,and the tomography image reveals the basic structure of the sample and it approves that it is feasible that thermal neutron tomography is developed by the uses of the thermal neutron radiography facility in No.300 reactor and it is ready for future work.

Evaluation of Wireless Communication Techniques for Portable PET Systems

ZHU Jun, ZHANG Bo, ZHANG Zhi, XIE Qing-guo

2007, 16(3): 50-59.

Abstract(784) PDF(1)

Abstract:
We evaluate the use of available wireless communication techniques in market for a portable Positron Emission Tomography(PET) system.For Wi-Fi,as well known as IEEE 802.11,our result shows that the total communication rate approximates the sum of data rates transferring through 3 independent channels in a limited space room.By use of a router implemented with 802.11g,98.21% and 34.66% average channel efficiencies are achieved for independent channels and non-independent channels,respectively.The results show the potential use of the Wi-Fi technique for a high-speed data communication in a PET system.We also discuss the potential use of Ultra Wide Band,Bluetooth,and Zigbee as a wireless communication implementation for a portable PET system.

Investigation of blood-brain barrier damage using delayed scan after CT perfusion imaging

YANG Chun, XU Kai

2007, 16(3): 60-64.

Abstract(755) PDF(0)

Abstract:
Objective. To study the changes of delayed scan after CT perfusion imaging in the right middle cerebral artery occlusion of rats,combining with histologic outcomes(light and electron microscopy).To investigation of blood-brain barrier damage after acute ischemic stroke.Methods. All 25 rats were divided into 5 groups.And the MCAO(middle cerebral artery occlusion) model were set up.Every groups performed routine scan,CT perfusion imaging(CTPI),and delayed scan in turn.All rats were killed immediately after scan and dealt with light and electron microscopy.Results. In group A,no abnormal outcomes were found in delayed scan.In group E,enhancement in the ipsilateral cortex in delayed scan were seen.And in light and electron microscopy most neurons were markedly shrunken,some of them had pyknotic nuclei and eosinophilic cytoplasm.Conclusion. Delayed scan can evaluate blood-brain barrier damage of acute ischemic stroke.

Diagnosis Obstructive Ureter by MSCT

LIN Shan, LI Kun-cheng, XU Wei, CAO Li-zhen

2007, 16(3): 65-70.

Abstract(621) PDF(0)

Abstract:
To analyze the manifestations of the ureter obstruction on MSCT.Seventy-six patients with obstructive ureter confirmed by surgery and pathology were reviewed.76 cases were correctly diagnozed by MSCT,in which 75% were common diseases(ureter calculi、carcinoma),25% were uncommon diseases.CT can clearly demonstrate the location and causes of the ureter obstruction and its relationship with around structures and play an important role in the diagnosis of ureter obstruction.

Application of 64-slice Spiral CT in the Diagnosis of Moyamoya Disease

ZHANG Xiu-li, ME Gang, LIU Ying

2007, 16(3): 71-75.

Abstract(924) PDF(1)

Abstract:
Objective: To study the value of 64-slice Spiral CT angiography in the diagnosis of Moyamoya disease.Material and methods: SCTA findings of 12 cases with Moyamoya disease were analyzed.In 12 cases,Male 5 and Female 7 were studied,age ranged from 16-72years.12 patients with Moyamoya disease were examined both with routine CT scanning and CTA,all performed Volume Rendering(VR),Maximum Intensity projection(MIP),Multi-planar(MPR).Results: Moyamoya vessels which were located in basal ganglia region.Cerebral hemorrhage was found in 9 cases.CTA showed the stenosis or occlusion of arteria and abnormal vessel network.VR was better on showing the stenosis of the vessels and its spatial relation with surrounding structure,MIP and MPR were better on showing abnormal vessel network in brain basal part and branch vessels.Stenosis or occlusion of the Distal portion of the ICA,Proximal portion of the ACA or MCA,and moyamoya vessels of basal ganglia region were demonstrated by DSA(n=6).Conclusion: 64-slice Spiral CT is of great value in the diagnosis of Moyamoya disease.

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2007 Vol. 16, No. 3